DE 196 27 752 A1 discloses an electric toothbrush comprising a handle and a brush part. An electric motor is located in the handle. A drive shaft protrudes from the handle and may be coupled to the electric motor. A brush part can be attached to the handle. The brush part further comprises a carrier for the bristles, which may be mechanically coupled to the drive shaft. When in operation the carrier for the bristles performs a rotational motion as well as a translational or swinging motion wherein the frequency of the swinging motion is larger than the frequency of the rotational motion.
In order to avoid damages when the contact pressure between the bristles and the user's teeth exceeds a certain predetermined value DE 196 27 752 A1 further describes that the swinging motion of the carrier for the bristles is interrupted when the contact pressure exceeds a certain predetermined value. As the interruption of the swinging motion according to DE 196 27 752 is achieved mechanically by disengaging an eccentric providing the swinging motion of the drive shaft an acoustical or optical signalling of the contact pressure exceeding a critical value to the user is achieved by mechanically activating an electrical switch.